Can't retrieve email from client

Hi Guys.
I can't find a similar thread to this.
Up until about 4 days ago my email was working fine.
Then I couldn't retrieve email.
I checked the mailboxes and there is recent mail in them, so it is receiving fine, and putting the mail in the correct boxes.
When I try to retrieve the email with a client it logs in OK, but doesn't get any email.
When I try https://mydomain:81/mailuser I get a "can't connect error" (same with webmail) however I am able to log in to ISPConfig as admin on port 81.
I have run Postfix check and get no errors.
Any suggestions?
TIA
Cambo

The last two were me trying to test Postfix.
I checked /etc/postfix and all of my domains and users are there.
The incoming email is in /home/www/web(No)/user/web(No)_(user)/Maildir/new
the /cur and /tmp folders are empty.
Thanks
Cambo

Hi Till
I have installed the whole system exactly as detailed in the Mandriva 2006 Perfect Install and the installation instructions of ISPConfig. I haven't modified anything as you guys know a lot more about it than me. What is the default? I did a "locate" for courier and dovecot and got no result (apart from courier font). If I "locate" pop I see /usr/sbin/ipop3 and ipop3s and ipop2.
/usr/sbin/ipop3d results in:
+OK POP3 webserver.mydomain.com 2004.89mdk server ready
/usr/sbin/imapd results in:
* OK [CAPABILITY IMAP4REV1 LITERAL+ SASL-IR LOGIN-REFERRALS AUTH=LOGIN] webserver.mydomain.com IMAP4rev1 2004.357mdk at ...

The thing is that everthing was working fine and then just stopped.
The only change I can remember making in the last week or so was adding a co-domain to one of my domains. That was mail.mydomain.com so that I could put that in my MX record in the DNS (Zoneedit, not local. I am not serving DNS to the Internet from this server.) The domain that I changed is not the main one that I use for email.
Regards
Cambo

Hi Till
Now we are getting somewhere. It was ticked.
I don't remember checking that box, but then again I don't remember what I had for dinner yesterday either.
I have unchecked it and saved it. Do I have to restart anything?
and where are the mail boxes now?
Thanks
Cambo

Hi Till
Now we are getting somewhere. It was ticked.
I don't remember checking that box, but then again I don't remember what I had for dinner yesterday either.
I have unchecked it and saved it. Do I have to restart anything?

Click to expand...

No

and where are the mail boxes now?

Click to expand...

/var/spool/mail

But you wont be able to retrieve the emails that has been send to your server in the meantime, because they are stored in a format that cn not be read by ipop3d.